1. Field of the Invention
This invention relates to an analog-to-digital conversion circuit. More particularly, this invention relates to an analog-to-digital conversion circuit which includes a sigma-delta modulator.
2. Brief Description of the Related Technologies
Converting analog signals to digital signals is accomplished using an analog-to-digital converter (ADC). An ADC circuit commonly contains a sigma-delta modulator circuit which is used to oversample an analog input signal so that it can more precisely be converted to a digital output signal. A decimation filter is typically required to follow the sigma-delta modulator circuit to down-sample the digital signal output from the sigma-delta modulator to the Nyquist sample rate with minimal added noise or distortion.
Existing ADC circuits utilize single stage decimation circuits which utilize coefficients to arrive at a certain frequency response, in order to gain more precision, for the circuit. As the number of coefficients increases, the number of on a one-stage decimation filter also increases so that for large numbers of coefficients a one-stage decimation filter becomes very complex and expensive to manufacture. Thus, the need arises for a high precision, analog-to-digital conversion circuit which is very precise yet relatively inexpensive to manufacture.